Angry Upper East Side protesters forced Mayor Bill de Blasio to relocate a press conference Sunday afternoon not once, but twice, as he was trying to announce more than $100 million in funding for new flood-proof boilers in city public housing complexes affected by Hurricane Sandy.

A few dozen residents, who railed against the proposal for a marine transfer station on East 91st Street, first caused de Blasio and US Sen. Chuck Schumer (D-NY) to move the announcement indoors to a community center in the Isaacs Houses on East 93rd Street.

But the protesters — demanding to be heard — just took their signs to the windows of the community room, prompting the mayor to move the presser into a hallway.

“I thought it was a very surprising thing to do,” neighbor Stephen Gross said about the move indoors.

“People are out here to show their signs. To move it inside is avoiding the public.”

De Blasio and Schumer said that NYCHA residents in about 8,000 apartments would benefit from the new storm-proof boilers. They will replace the temporary boilers that have been plagued with problems.

But protesters argued that the flood-prone area did not make for a good location for a waste transfer station.

“This is a flood zone,” said Fred Cannizzaro. “I watched the water come up to First Avenue. So you really have to ask yourself, ‘Why they are building it in a flood zone?’”

The transfer station, which closed-down in 2009, is slated to reopen in 2016. De Blasio called for a “five borough plan” to deal with the city’s waste.

“We believe this is a very important project for the city,” the mayor said about the waste transfer station.

“They have the right to have their voices heard. We’re going to work with the community.”